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Abstract:

When estimating an arterial input function or a patient under study,
cross-calibration factors are generated by comparing nuclear scan data of
a radioactive material (e.g., F18) and measuring a sample of the
radioactive material in a gamma counter. The derived cross-calibration
factors are applied to venous samples collected from the patient during a
nuclear scan after infusion with a radioactive tracer, to convert gamma
values counted by the gamma counter into concentration values. The
concentration values are used to optimize an initial estimated input
function, thereby generating an arterialized input function.

Claims:

1. A system that facilitates cross-calibrating a nuclear scanner to a
gamma counter, including: a nuclear scanner that scans a radioactive
calibration phantom comprising a radioactive material to acquire scan
data; a gamma counter that measures a radioactivity level of a sample of
the radioactive material to acquire measurement data; a processor that
executes computer-executable instructions stored in a memory, the
instructions including: generating one or more cross-calibration factors
from the scan data and the measurement data.

2. The system according to claim 1, wherein the instructions further
include: acquiring patient scan data of a patient in list mode;
generating reconstructed series of nuclear images by reconstructing the
list mode data in each of a series of temporal sampling windows;
identifying arterial regions in the nuclear images; and generating an
initial time-activity curve (TAC) based on nuclear image data in the
identified arterial regions.

3. The system according to claim 2, wherein the instructions further
include: iteratively adjusting the sampling window and reconstructing the
series of images; determining a sampling window in which early bolus
activity in the TAC provides a predetermined level of accuracy.

4. The system according to claim 2, wherein the instructions further
include: measuring venous samples in the gamma counter, the venous
samples being collected from the patient at determined intervals during
the patient scan data acquisition; and converting radioactivity level
information in the venous samples to concentration values.

5. The system according to claim 4, wherein the instructions further
include: correcting the initial TAC using the radioactivity level
information from the venous samples; and outputting an arterialized input
function to at least one of a display for presentation to a user and a
memory for storage or usage in pharmacokinetic studies.

6. The system according to claim 2, wherein the nuclear scanner is a
multi modal positron emission tomography (PET)/computed tomography (CT)
scanner and the acquired patient scan data includes and PET scan data and
CT scan data.

7. The system according to claim 2, wherein an initial width of the
sampling window is in the tame of 5 to 15 seconds.

8. The system according to claim 2, wherein venous samples are collected
from the patient during a nuclear scan and approximately 1-2 minutes
after infusing the patient with a radioactive tracer.

9. The system according to claim 1, wherein the wherein the radioactive
material includes fluorodeoxyglucose 18 (18F).

10. A method of optimizing an plasma input function for a patient under
study, including: scanning a radioactive calibration phantom comprising a
radioactive material to acquire nuclear scan data; measuring a
radioactivity level of a sample of the radioactive material to acquire
measurement data; and generating one or more cross-calibration factors
from the scan data and the measurement data.

11. The method according to claim 10, further including: acquiring
patient scan data of a patient in list mode; generating a series of
nuclear images by reconstructing the list mode data in each of a series
of temporal sampling windows; identifying arterial regions in the nuclear
images; and generating an initial time activity curve (TAC) based on
nuclear image data in the identified arterial regions.

12. The method according to claim 11, further including: iteratively
adjusting the sampling window and reconstructing the series of images;
determining a sampling window in which early bolus activity in the TAC
provides a predetermined level of accuracy.

13. The method according to claim 11, further including: measuring venous
samples in the gamma counter, the venous samples being collected from the
patient at determined intervals during the patient scan data acquisition;
converting radioactivity level information in the venous samples to
concentration values.

14. The method according to claim 13, further including: correcting the
initial TAC using the radioactivity level information from the venous
samples; and outputting an arterialized input function to at least one of
a display for presentation to a user and a memory for storage or usage in
pharmacokinetic studies.

16. The method according to claim 11, wherein an initial width of the
sampling window is in the range of 5 to 15 seconds, and wherein venous
samples are collected from the patient during a nuclear scan and
approximately 12 minutes after infusing the patient with a radioactive
tracer.

17. The method according to claim 10, wherein the wherein the radioactive
material includes fluorodeoxyglucose 18 (18F).

18. A processor or computer-readable medium carrying a computer program
that controls one or more processors to perform the method of claim 10.

19. A method of optimizing a plasma input function for a patient under
study, including: acquiring positron emission tomography (PET) scan data
of a patient in list mode; reconstructing the acquired PET scan data into
a nuclear image; identifying arterial regions in the nuclear image;
assessing a sampling window for sampling early bolus activity in the
acquired PET scan data to determine whether the sampling window provides
a predetermined level of accuracy for generating an initial time-activity
curve (TAC); adjusting the sampling window when the sampling window does
not provide the predetermined level of accuracy; reconstructing
additional nuclear images when the sampling window provides the
predetermined level of accuracy; generating the initial TAC; collecting
venous samples from a patient during PET scan data acquisition after
infusing the patient with a radioactive tracer; measuring the venous
samples in a gamma counter; comparing radioactivity levels measured in
the gamma counter to levels indicated in the TAC; adjusting the TAC until
activity levels in the TAC coincide with activity levels measured in the
gamma counter; generating an arterialized input function (AIF) as a
function of the adjusted TAC; and outputting the AIF to at least one of a
display for presentation to a user and a memory for storage.

Description:

[0001] The present application finds particular application in positron
emission tomography (PET) systems, particularly involving arterial input
function estimation. However, it will be appreciated that the described
technique may also find application in other medical input function
estimation systems, other patient modeling scenarios, or other input
function estimation techniques.

[0002] Continued improvements in the hardware capabilities of current
generation medical imaging scanners have generated increased interest in
quantitative imaging. Accurate determination of changes in physiological
parameters during or at the completion of therapy is important in
determining the effectiveness of treatment. For example, PET imaging
incorporating pharmacokinetic modeling can provide absolute
quantification measures of metabolism, perfusion, and proliferation among
others. Monitoring changes in many of these parameters could lead to more
personalized treatment strategies, whereby ineffective therapies could be
altered or discontinued early on and alternative treatments offered. If
pharmacokinetic modeling techniques are employed for absolute
quantitative measurements, an accurately measured input function is
important.

[0003] While qualitative (visual) impressions of PET uptake are useful in
identifying/detecting the presence of cancer or other conditions, there
is a clear need in the art for accurate and reproducible quantification
of the uptake of an injected pharmacological tracer, e.g.
fluorodeoxyglucose (FDG), at suspected sites, during the course of
treatment to evaluate treatment effectiveness. This can be done by
measuring relative changes in the tracer uptake over time and correlating
this to other measures of clinical response.

[0004] In PET imaging, the current clinical paradigm towards a more
objective uptake measure is to use the semi-quantitative standard-uptake
value (SUV) taken at a given point in time after tracer injection
(typically 50-60 min post-injection). The SUV measure, while easy to use
clinically, is affected by a large number of factors including, time of
acquisition, lack of specificity between metabolized and un-metabolized
tracer, as well as variable blood pool clearance. Dynamic imaging
initiated at the time of tracer injection, in combination with modeling
of the acquired time-activity-curves (TAC), i.e. the underlying
pharmacokinetics, provides the ability to make quantitative measurements
of processes such as metabolism, hypoxia, proliferation and perfusion.
There is growing evidence that kinetic analysis may be superior to
standard techniques in evaluating treatment response.

[0005] As mentioned previously, accurate quantification depends strongly
on the quality of the measured blood (plasma) input function. One
approach is to acquire a number of arterial blood samples (i.e., an
arterial input function) during the dynamic study. However, this
procedure is not used routinely due to patient safety considerations.
Moreover, getting institutional review board (IRB) approvals for clinical
studies including arterial blood sampling can be very challenging.

[0006] An alternate approach is to use image-derived input functions by
placing regions-of interest (ROIs) in the blood pool (e.g. left
ventricle, aorta). However, considerations such as limited scanner
resolution and sub-optimal temporal sampling of the resultant TAC will
affect the quality of the image-derived input functions as explained
below.

[0007] Thus, in nuclear imaging, it is desirable to derive a quantitative
measure of the underlying physiological processes such as metabolism or
proliferation. This can be achieved by using kinetic modeling techniques
which requires an accurately measured blood input function. After
administration of a radioactive tracer to a subject, the bolus of
activity usually peaks within the first minute and rapidly decreases and
levels off to a background level over time. This input function can be
measured by collecting a plurality of arterial blood samples at short
time intervals during the early part of the scan, followed by sparsely
sampled measurements for the remainder of the scan. However, arterial
blood sampling is not good clinical practice due to safety and patient
comfort considerations. Instead, it is customary to generate an image
focused on arterial blood to use as a reference. However, this approach
has two drawbacks. First, due to limited scanner resolution, pixels
depicting the arterial blood tend to be inaccurate, sampling not just the
blood but also surrounding tissue. Second, the coarse temporal sampling
will reduce the apparent peak amplitude of the input function, resulting
in incorrect kinetic model estimates.

[0008] The present application provides new and improved systems and
methods for optimizing an input function during a nuclear scan, which
overcome the above-referenced problems and others.

[0009] In accordance with one aspect, a system that facilitates
cross-calibrating a nuclear scanner to a gamma counter includes a nuclear
scanner that scans a radioactive calibration phantom comprising a
radioactive material to acquire scan data, and a gamma counter that
measures a radioactivity level of a sample of the radioactive material to
acquire measurement data. The system further includes a processor that
executes computer-executable instructions stored in a memory, the
instructions including generating one or more cross-calibration factors
from the scan data and the measurement data.

[0010] In accordance with another aspect, a method of optimizing an plasma
input function for a patient under study includes scanning a radioactive
calibration phantom comprising a radioactive material to acquire nuclear
scan data, measuring a radioactivity level of a sample of the radioactive
material to acquire measurement data, and generating one or more
cross-calibration factors from the scan data and the measurement data.

[0011] In accordance with another aspect, a method of optimizing a plasma
input function for a patient under study includes acquiring positron
emission tomography (PET) scan data of a patient in list mode,
reconstructing the acquired PET scan data into a nuclear image, and
identifying arterial regions in the nuclear image. The method further
includes assessing a sampling window for sampling early bolus activity in
the acquired PET scan data to determine whether the sampling window
provides a predetermined level of accuracy for generating an initial
time-activity curve (TAC), adjusting the sampling window when the
sampling window does not provide the predetermined level of accuracy, and
reconstructing additional nuclear images when the sampling window
provides the predetermined level of accuracy. Additionally, the method
includes generating the initial TAC, collecting venous samples from a
patient during PET scan data acquisition after infusing the patient with
a radioactive tracer, measuring the venous samples in a gamma counter,
and comparing radioactivity levels measured in the gamma counter to
levels indicated in the TAC. Furthermore, the method includes adjusting
the TAC until activity levels in the TAC coincide with activity levels
measured in the gamma counter, generating an arterialized input function
(AIF) as a function of the adjusted TAC, and outputting the AIF to at
least one of a display for presentation to a user and a memory for
storage.

[0012] One advantage is that input function estimation is improved.

[0013] Another advantage resides in minimizing invasiveness of the blood
sampling procedure.

[0014] Still further advantages of the subject innovation will be
appreciated by those of ordinary skill in the art upon reading and
understand the following detailed description.

[0015] The innovation may take form in various components and arrangements
of components, and in various steps and arrangements of steps. The
drawings are only for purposes of illustrating various aspects and are
not to be construed as limiting the invention.

[0016] FIG. 1 illustrates a system for generating arterialized
image-derived input functions used in kinetic analysis and therapy
efficacy evaluation, in accordance with one or more aspects described
herein.

[0018]FIG. 3 illustrates a method for generating cross-calibration
factors that facilitate calibrating a nuclear scanner, such as a PET or
SPECT scanner, in accordance with one or more aspects described herein.

[0019]FIG. 4 illustrates a method of refining an input function used for
kinetic modeling of dynamically acquired PET data, in accordance with one
or more aspects described herein.

[0020] The subject innovation overcomes the aforementioned problems in the
art by acquiring scan data in list-mode and retrospectively binning the
data to generate an image that includes the arterial region. When data is
collected in the list mode, the raw data is stored in a list with each
entry carrying a time stamp denoting the time of acquisition. This keeps
the raw data available for later analysis or reuse (e.g.
re-reconstructed) even after the diagnostic image has been reconstructed.
Because the data is collected and stored in list-mode, the size of the
temporal bin can be retrospectively adjusted and the process repeated for
different size or temporarily shifted bins until the true peak is
determined. During the imaging process, as blood samples are drawn and
the concentration of the tracer in the samples is measured empirically.
Because these samples are drawn relatively late in the imaging process,
the concentration of the radiopharmaceutical in the arteries and the
blood vessels has substantially equalized. The plurality of samples taken
at known times are used to scale or adjust a curve of arterial blood
concentration versus time in order to calibrate the true arterial input
function.

[0021] The herein-described systems and methods provide a streamlined,
integrated work-flow for generating arterialized image-derived input
functions for kinetic analysis of novel tracers. The entire sequence of
acquisition (dynamic image acquisition, venous blood sampling, etc.) and
processing steps such as optimized reconstruction protocol, contouring
arterial regions in the image, correcting the image derived input
function for sub-optimal temporal sampling, as well as partial volume and
spillover effects, are all implemented on the same platform, greatly
simplifying the procedure.

[0022] FIG. 1 illustrates a system 100 for generating arterialized
image-derived input functions used in kinetic analysis and therapy
efficacy evaluation, in accordance with one or more aspects described
herein. Accurate determination of changes in physiological parameters
during or at the completion of therapy is important in personalized
therapy in order to determine the effectiveness of treatment. For
example, PET dynamic imaging incorporating pharmacokinetic modeling can
provide absolute quantification measures of metabolism, perfusion, and
proliferation among others. Monitoring changes in these parameters during
the course of therapy can provide a measure of treatment response,
whereby ineffective therapies can be adapted or discontinued early on and
alternative treatments can be offered. The successful incorporation of
these imaging biomarkers for predicting treatment response strongly
depends on their accuracy and reproducibility. The accuracy of these
quantitative measurements depends on the quality of the measured plasma
input function. The described innovation provides streamlined, integrated
systems and methods for generating arterialized image-derived input
functions used in kinetic analysis.

[0023] The system 100 includes a nuclear medicine scanner (e.g., PET or
SPECT) 102, which scans a phantom 103 to acquire raw emission data that
is used to calibrate the scanner. The nuclear medicine scanner is also
used to scan a subject or patient to scan raw data of the subject or
patient. A reconstruction processor 104 reconstructs the raw data into an
emission image of one or more anatomical structures (i.e., a volume of
interest) in the patient. The system further includes a processor 105
that executes, and a memory 106 that stores, computer-executable
instructions for performing the various acts, functions, methods
techniques, procedures, etc., described herein. The memory 106 also
stores the list mode data. Additionally, the system 100 includes a user
interface 108 that comprises a user input device 110 (e.g., a keyboard,
microphone, stylus, mouse, touch pad, touch screen, etc.) by which a user
enters information into the system, and a display 112 on which
information is presented to the user.

[0024] As is known in the art, when an electron and positron meet, they
annihilate, emitting two 511 keV gamma rays that are oppositely directed
in accordance with the principle of conservation of momentum. In PET data
acquisition, two substantially simultaneous or coincident 511 keV gamma
ray detection events are presumed to have originated from the same
positron-electron annihilation event, which is therefore located
somewhere along the "line of response" (LOR) connecting the two
substantially simultaneous 511 keV gamma ray detection events. This line
of response is also sometimes called a projection, and the collected PET
data is referred to as projection data.

[0025] In conventional PET, two 511 keV gamma ray detection events
occurring within a selected short time or coincidence window, such as
within 6 nanoseconds of each other, are taken as defining a valid LOR.
Due to the variable annihilation position with respect to the detector
elements a small (e.g., sub-nanosecond) time difference between the
coincident gamma photon detection events occurs. A related technique,
called time-of-flight PET or TOF-PET, takes advantage of this small time
difference to further localize the positron-electron annihilation event
along the LOR. In general, the annihilation event occurred along the LOR
at a point closer to the gamma ray detection event that occurred first.
If the two gamma ray detection events occur simultaneously within the
time resolution of the detectors, then the annihilation event occurred at
the midpoint of the LOR. The two detection events that define each LOR
are stored, with their respective time stamps, in the memory 106 in the
list-mode.

[0026] As stated above, the system 100 includes the processor 105 that
executes, and the memory 106, which stores, computer-executable
instructions (e.g., routines, programs, algorithms, software code, etc.)
for performing the various functions, methods, procedures, etc.,
described herein. Additionally, "module," as used herein, denotes a set
of computer-executable instructions, software code, program, routine, or
the like, as will be understood by those of skill in the art.

[0027] The memory may be a computer-readable medium on which a control
program is stored, such as a disk, hard drive, or the like. Common forms
of computer-readable media include, for example, floppy disks, flexible
disks, hard disks, magnetic tape, or any other magnetic storage medium,
CD-ROM, DVD, or any other optical medium, RAM, ROM, PROM, EPROM,
FLASH-EPROM, variants thereof, other memory chip or cartridge, or any
other tangible medium from which the processor can read and execute. In
this context, the systems described herein may be implemented on or as
one or more general purpose computers, special purpose computer(s), a
programmed microprocessor or microcontroller and peripheral integrated
circuit elements, an ASIC or other integrated circuit, a digital signal
processor, a hardwired electronic or logic circuit such as a discrete
element circuit, a programmable logic device such as a PLD, PLA, FPGA,
Graphical card CPU (GPU), or PAL, or the like.

[0028] The system 100 further includes a cross-calibration module or
processor 120, which executes an algorithm or workflow for
cross-calibrating the nuclear scanner 102. For instance, when the nuclear
scanner is a multi-modal scanner that acquires both PET and computed
tomography (CT) data, then at 122, PET/CT data acquisition is performed
by scanning a radioactive phantom with a known radioactivity
concentration. At 124, a sample vial with a radioactivity level that is
the same as that of the phantom is measured in a gamma counter 125. At
126, cross-calibration factors are generated from the acquired PET/CT
data and the measurement data provided by the gamma counter.

[0029] The system 100 also includes an input function generator or
processor 140 that executes an algorithm or workflow for optimizing an
input function, in accordance with various aspects described herein. For
instance, at 142, the scanner 102 is controlled to acquire PET/CT data by
scanning a patient and storing the acquired data in list mode. At 144, an
intermediate reconstruction is performed to generate an intermediate
image of the patient. At 146, a determination is made regarding whether a
sampling rate or window for sampling early bolus activity is sufficient
to provide a desired predetermined level of accuracy for generating an
initial input function. If not, then the sampling rate or window is
adjusted by looking at the time stamps to select a different length for
time shifted sampling windows, at 148. The workflow reverts at 146 to
reconstruct the re-binned list mode data is used to generate another
intermediate reconstructed image but with a different, e.g. shorter,
sampling window than the first intermediate image. When the sampling rate
or window is satisfactory (i.e., when a user is satisfied with the
accuracy of the intermediate reconstructed image), a final reconstruction
of the PET image is generated, at 150. At 152, arterial regions in the
final PET image are manually or automatically identified and the system
generates an initial input function. The user interface 108 is used to
manually identify the arterial region(s) or for a user to verify on
automatic identification.

[0030] At 154, venous samples are collected from the patient during the
PET scan at predetermined intervals, typically sufficiently late in the
study that concentrations in the arteries and veins have equilibrated. At
156, vials containing the venous samples are measured in the gamma
counter 125. At 158, measured venous sample measurement data collected at
156 is converted to activity/concentration units using the
cross-calibration factor(s) generated at 126 by the cross-calibration
module 120. At 160, the initial input function is adjusted to correct for
partial volume and spillover effects. At 162, an arterialized (final)
input function is output. The arterialized input function, as well as any
other data generated by the system 100 and/or components thereof is
stored in the memory 106 and can be recalled or accessed by the user for
viewing on the display 112.

[0031] With regard to the effect of scanner resolution on image-derived
input functions, partial volume effects due to limited scanner resolution
and spillover of activity from nearby structures can affect the overall
shape of the input function. A number of investigators have looked into
this problem and shown that by calibrating the image-derived input
function against a few late-time venous blood samples (typically 3
samples), the estimated initial input function can be "arterialized".
See, e.g., Chen, K., et al., Characterization of the image-derived
carotid artery input function using independent component analysis for
the quantitation of [18F] fluorodeoxyglucose positron emission tomography
images. Phys Med Biol, 2007. 52(23): p. 7055-71. See also, e.g.,
Hoekstra, C. J., O. S. Hoekstra, and A. A. Lammertsma, On the use of
image-derived input functions in oncological fluorine-18
fluorodeoxyglucose positron emission tomography studies. Eur J Nucl Med,
1999. 26(11): p. 1489-92. These have shown that the addition of a few
venous blood samples provides similar results to an arterial sampled
input function. Moreover, collecting 3 venous blood samples (1 ml in
volume) late in the dynamic acquisition is less invasive and safer for
the patients than a protocol which involves arterial sampling.

[0032] Accordingly, in one embodiment, the system 100 is employed to
perform quality control and calibration for image derived input
functions. For instance, several (e.g., three) venous blood samples can
be collected, each approximately 1 ml in volume, towards the end of the
dynamic acquisition scan. Radioactivity in the vials is counted using the
gamma counter 125, such as a Packard Cobra® Gamma Counter. The
cross-calibration factor is applied between the gamma counter and PET
scanner to convert venous sample activity to concentration units (Bq/cc).
Finally, partial volume and spillover corrections are applied to
image-derived input function using the venous blood samples. In this
manner, the system 100 provides a systematic framework that improves the
quality of input function estimation resulting in reliable and accurate
measurement of physiological parameters, subsequently enabling accurate
prediction of treatment response in patients.

[0033]FIG. 2 illustrates optimal and sub-optimal temporal sampling of an
image derived input function. When the early activity (e.g., less than 50
seconds) for the TAC 182 is sampled every 10 seconds, it exhibits an
impulse-like shape. When the same data is initially sampled only every 30
seconds, such as is the case for the TAC 184, a significant reduction in
the magnitude of the peak as well a peak shift in time is observed.
Coarse temporal sampling thus reduces the magnitude (height) of the input
function peak, which can result in an incorrect kinetic model estimates
(e.g., FDG influx rate, cerebral blood flow). In older generation PET
scanners, the temporal sampling scheme for dynamic studies was fixed
prior to acquisition with no recourse to changing the sampling scheme
once the acquisition was complete. This was mainly due to the fact that
raw data was binned and stored as 4D sinograms due to storage and memory
considerations. However, current generation scanners such as the
GEMINI® TF PET/CT scanners from Philips Medical Systems store the data
in list mode, making it possible to change the temporal sampling,
especially early in the course of tracer distribution through the
arterial and venous systems.

[0034] When using a long sampling window (e.g., 30 seconds), there is
ample data in for reconstruction in each window, but the count rate is
averaged over a longer period, and therefore magnitude of the TAC may be
reduced. When using a short sampling window (e.g., 10 seconds), high
temporal resolution of the count rate is achieved, but a scarcity of data
in each window can cause artifacts to degrade the reconstructed image.
Accordingly, the described systems and methods relate to adjusting
sampling window settings to optimize the TAC curve. In this manner, an
optimized sampling window can be identified, which is sufficiently long
to permit a satisfactory image quality and sufficiently short to achieve
high temporal resolution of the count rate. In one embodiment,
approximately three venous samples are used, along with the artery volume
image values at the same times, to scale the amplitude of the TAC.

[0035] FIGS. 3 and 4 illustrate a methods related to refining an input
function used for kinetic modeling of acquired PET data, in accordance
with various features. While the methods herein are described as a series
of acts, it will be understood that not all acts may be required to
achieve the described goals and/or outcomes, and that some acts may, in
accordance with certain aspects, be performed in an order different that
the specific orders described.

[0036]FIG. 3 illustrates a method for generating cross-calibration
factors that facilitate calibrating a nuclear medicine scanner, such as a
PET or SPECT scanner, in accordance with one or more aspects described
herein. At 200, emission data is acquired from a phantom that contains a
sample, e.g. vial of the tracer. In one embodiment, the tracer is an 18F
(fludeoxyglucose-18) tracer. An emission image is reconstructed from the
acquired emission data and a subvolume of the image corresponding to the
sample vial is identified, at 202. At 204, an image value indicative of
the activity level in the subvolume corresponding to the sample vial is
determined. At 206, the activity level of the sample in the vial is
measured in the gamma counter 125. At 208, a cross-calibration factor is
determined between the activity levels as measured by the gamma counter
125 and PET/CT scanner image values. At 210, the procedure is optionally
iterated on a periodic basis (e.g., monthly, quarterly, etc.) to verify
the cross-calibration factor.

[0037]FIG. 4 illustrates a method of refining an input function used for
kinetic modeling of dynamically acquired PET data, in accordance with one
or more aspects described herein. At 220, PET data is acquired in
list-mode format. At 222, the data is reconstructed with a nominal
sampling/binning window to generate a series of images at short terminal
intervals. At 224, the time and activity curve (TAC) of FIG. 2 is
determined for the early bolus activity in the arterial volume. At 226,
the sampling/binning window width is adjusted, e.g. shortened, and the
reconstruction is repeated. In one embodiment, the temporal width of the
sampling in the initial 60-120 seconds is chosen such that a predefined
noise-level is not exceeded. Based on decay statistics, this may lead to
a sampling window of e.g. 10 s, although other sampling window widths or
ranges thereof are contemplated (e.g., 5 s, 15 s, 20 s, etc.). The
sampling window is iteratively adjusted at 228 until the early bolus
activity exhibits a sharp peak or is otherwise optimized. Additional
images, e.g. a series of diagnostic images, are generated at 230 over the
course of the emission study, typically with a sampling window dictated
by the nuclear imaging protocol. The arterial volume continues to be
monitored and the TAC is adjusted and/or plotted at 224.

[0038] At 232, venous blood samples are collected at known time points,
sufficiently long into the nuclear imaging study that the activity in
arterial and venous blood as equalized. At 234 the activity level in
blood samples is measured with the gamma counter 125. In one embodiment,
the user interface 108 (FIG. 1) prompts a technician or user to collect
venous samples at specific times, count activity of blood samples in the
gamma counter 125. At 236 the activity level as measured from the TAC
curve at the time the blood samples were taken are compared with the
activity levels measured by the gamma counter 125. At 238, the TAC is
scaled to bring the activity levels of the TAC into coincidence with the
activity levels measured by the gamma counter. At 240, the finalized
arterial input function (AIF) is generated and at 242 the AIF is used for
kinetic modeling of the acquired dynamic nuclear study data.

[0039] The innovation has been described with reference to several
embodiments. Modifications and alterations may occur to others upon
reading and understanding the preceding detailed description. It is
intended that the innovation be construed as including all such
modifications and alterations insofar as they come within the scope of
the appended claims or the equivalents thereof.

Patent applications by Jens-Christoph Georgi, Aachen DE

Patent applications by Manoj Narayanan, Snohomish, WA US

Patent applications by KONINKLIJKE PHILIPS ELECTRONICS N.V.

Patent applications in class Combined with therapeutic or diagnostic device

Patent applications in all subclasses Combined with therapeutic or diagnostic device